In today's urban environments, many people live or work in multi-storied buildings such as sky-scrapers. In case of a fire or terrorist attack, rapid descent from upper floors of such buildings may be necessary. In such emergency situations, use of an elevator may be unsafe. Emergency stairwells may become blocked by fire or smoke, making rapid escape difficult. Descent devices may be used in such emergency situations to allow a rescuee to be safely lowered to the ground.
Some patent publications relating to brake mechanisms usable for controlled descent device (CDD) applications are briefly described below.
US Patent publication No. 2010/181145 describes a descent device comprising a hollow spool rotatable about a rotational axis and a lifeline, in the form of a braided steel cable, wound about the spool. A centrifugal brake mechanism including a brake assembly, comprising a pair of brake shoes and associated brake pads, is engageable with the spool to apply a braking force to the spool as the spool rotates. Biasing members, in the form of compression springs, extend between the brake shoes for biasing the brake shoes and pads into engagement with the spool.
US Patent publication No. 2004/245048 describes a rappelling device for permitting persons to be rescued from high buildings, towers, and the like, having a suspension strap, suspension vest, or the like, to be worn by the person in question, wherein a rope container having a device to release the rope length is provided on the suspension strap, which solution is supposed to be easy to operate, on the one hand, and to be made available to the persons in question at any time, and easy to handle for them, whereby the person using the device can essentially move both hands freely, in a stable rappelling position. This is achieved in that the rope drum that forms the rope container, in the wearing position on the back of the person using the device, is provided with a rope guide device for passing the rope to a release position in the chest region of the person using the device.
International Patent Publication No. WO 03/055560 discloses an abseiling device used as rescue equipment in disaster situations, particularly fires in buildings or tall buildings, comprising a harness for supporting particularly a person, a housing provided with a rope drum and an automatic braking device, and a rope, one end of which is fixed to the building and the other end of which is fixed to the housing. The housing is connected to the harness so as to form a unit.
International Patent Publication No. WO 89/00063 describes a lowering device particularly for assisting persons to escape from multi-storied buildings in an emergency situation, and adapted to engage a cable or rope of twisted configuration. The device comprises an inner rotatable sleeve surrounding and engaging the cable to follow the twist therein and rotate about the cable as it descends down the cable. The inner sleeve is contained within an outer housing which, in turn, supports a person, and the speed of rotation of the inner sleeve and thus the rate of descent of the device down the cable is controlled by a centrifugal brake having bell cranks carried by the inner sleeve and each pivotable against tension springs under centrifugal force to cause eccentrics on the ends of the cranks to act on brake shoes which engage a brake surface on part of the outer housing. Also disclosed is a device which, as an alternative, involves braking by utilizing a hydraulic system with a closed circuit gear pump driven by the inner sleeve and containing a variable constricted orifice to control the speed of the pump and therefore the rate of descent of the device.
The slow descender described in U.S. Pat. No. 3,946,989 includes a rope pulley and a braking apparatus which restricts the rotation speed of the rope pulley. The braking apparatus includes a mechanical braking device containing a centrifugal brake which has centrifugal weights, a V-shaped lining part cooperating with the weights, and a speed multiplying gearing device connecting the rope pulley and the centrifugal friction brake. The slow descender further includes an oil hydraulic braking device of the vane pump type or of the inscribed gear pump type.
U.S. Pat. No. 4,986,390 describes a small and light slow-descending device that anybody can easily carry in a traveling bag, or the like. Therefore, it is useful as an emergency evacuation device which enables to escape from a fire in a hotel, apartment house, office building, etc., or from a disaster in a high level road or highway, etc.